The present invention relates generally to fluid control systems that redirect or vary fluid flow or contain flow regulating devices, or particularly to fluid flow control systems including fluid flow regulating devices for maintaining a constant flow within a specified range of accuracy with varying pressure differentials, and more particularly to fluid flow regulating devices that provide accurate or precise flow control over a specified range of pressure differentials, producing little if any air borne or structure borne noise during operation of the fluid system throughout its range of control.
Fluid flow regulating devices are currently used in a variety of fluid control applications for industrial, military, or commercial requirements. Specifically, cooling water flow control systems are used to maintain a pre-determined flow rate to assure efficient heat transfer and maintain safe temperature operating range. The same basic concept is used as a temperature control wherever either an ambient temperature or heat generated from power consumption must be controlled. The use of flow control in hydraulic systems permits accurate positioning, control or rate, or precision retraction or extension under conditions that may have varying load. Examples of this type of fluid flow control are found in power lines in service vehicles, hydraulic lifting systems, and steel/roll mills.
The invention can also be utilized in medical applications to accurately or precisely control flow for cooling including oxygen, breathing systems, dialysis, heart and angioplasty machines. The flow control may be either liquid or gas. A typical application would include a cooling of the helium gas used to expand and/or contract "the balloon" inserted into a blocked arterial area.
Both pressure and flow control devices can generate noise that can be carried from the point of generation through some distance by either the system structure, its mounting or the structure surrounded and attached to the pressure or flow control system. This generated noise can be detected at a distance whether the atmosphere is a gas or a liquid. The noise generated can be the result of cavitation, impingement, turbulence, or entrained gases in liquid. A typical example of gas entrained in liquid as a noise generation in a pressure/flow system is the air hammering caused in hot water heat systems or steel pipes. The air entrained in the water results in flow variations. A similar condition occurs in liquids that are allowed to flow at sufficiently high velocities resulting in a high pressure drop in areas where the fluid conduit or pipe becomes restricted or changes direction. The pressure drop causes the fluid in these areas to change from a liquid to a gas. When the fluid containing entrained gas bubbles travels to a point where the system's pressure returns to a high pressure the entrained gas bubbles or voids collapse. The collapse generates noise and can result in the deterioration of the containment located at this vicinity (cavitation). The noise level generated into the fluid system can cause discomfort, annoyance, or harm to local inhabitancies. Public utilities are concerned with eliminating the noise generated capacity of fluid systems in gas transportation lines and other fluid flow systems. The control of an acceptable noise level depends on whether the noise is being transported or carried at a structure or is being detected or carried in a liquid or gas. Air borne noise can be controlled or diverted by unique structure designs. Minimizing the noise generated depends upon the flow rate, pressures, and system design. The level of noise reduction and the selection of the components of the system will determine the envelope or achievable noise level reduction with specific frequencies.
A typical flow control device is an elastomeric flow restrictor. The flow restrictor deforms into a plastic flow element as a pressure differential increases across the restrictor. In these devices as the pressure differential increases so does the deformation of the flow restriction and/or element cutouts. These devices are limited in use to a narrow pre-determined set of pressures and flow rates. The use of these devices creates high velocities, turbulence, and can result in cavitation. Similarly, if the fluid contains particulate matter either intentional such as a catalytic process, or contains dirt or other contaminants, the high velocities will result in impingement damage. All of these conditions are known to be sources of noise generation in fluid (liquid or gas) control systems using flow control or pressure control devices.
For specific shipboard applications, flow regulator valves similar to those described above are typically used to balance the flow rate of water to and from heating and cooling coils when several coils are supplied from one pump incorporating many branches in the flow circuit. For this reason, the flow regulator valves are typically called balancing valves because they balance the flow rate of water to each coil, although they are often used to balance flow control rates for other applications. The valves are most often used to control the flow rates of fluids with viscosities similar to that of water to fixed flow rates with variations in pressure drop across the valves. Without a flow regulation valve, as the pressure drop across a fixed orifice is increased, the flow rate is increased accordingly.
One specific type of prior flow regulator device employed a resilient diaphragm, as in U.S. Pat. No. 3,189,125. In operation, the resilient diaphragm is forced against a contoured orifice as the fluid pressure drop increases across the valve. Increasing pressure drop across the valve will progressively press the resilient diaphragm against a contoured orifice, causing the flow area between the resilient diaphragm and the contour to be reduced. The reduction in flow area is sufficient to restrict the flow to a more-or-less constant value even though the pressure drop across the flow area has increased (see FIG. 14 of the '125 patent). Many of these existing balancing valves utilize ribs that are molded onto the resilient diaphragm to keep the resilient diaphragm concentrically centered in the flow path immediately upstream of the contoured orifice. See, e.g., U.S. Pat. Nos. 5,409,042; 5,027,861; 4,986,312; 3,189,125 and 3,958,603. In these patents, the fluid first flows around the front of the resilient diaphragm, then through the annular section between the walls of the flow passage and the resilient diaphragm. Next, the fluid is diverted into the flow section between the resilient diaphragm and the contoured orifice (the variable flow area section) then exits out the back of the contoured orifice. Fluid flow through these devices is converging rather than diverging.
Thus, there is a need for new and improved fluid flow control systems including new and improved fluid flow regulating/control devices that maintain a constant flow rate therethrough within a range of pressure differentials. Such fluid flow regulating/control devices for maintaining a constant flow rate should: (1) overcome the aforementioned problems; (2) accurately control the fluid flow rate over a wide range of differential pressures; (3) produce little, if any, air borne or structure borne noise during operation; (4) have as few parts as possible and (5) significantly reduce, if not eliminate, the tendency for the flow control element from becoming dislodged; (6) significantly reduce, if not eliminate, all sharp bends or abrupt changes in the fluid flow path throughout the device and (7) be economically manufacturable.